As a fluorescent colorant compound, various derivatives of rhodamine have been studied. In addition, as a compound prepared by condensing two rhodamine molecules, there has been known an aminobenzopyrano-xanthene colorant compound (Patent document 1). It is known that this aminobenzopyrano-xanthene compound exhibits three types of molecular structures which are a neutral form, a monocationic form and a dicationic form, depending on the hydrogen-ion concentration of a solution, and that each molecular structure leads to different absorption and emission properties (Non-patent document 1).